A toll-free telephone number is a telephone number that is billed for incoming calls rather than charging a caller of the toll-free telephone number for placing the call. Thus, a caller may call the toll-free telephone number without being charged for the call. Toll-free numbers may begin with a prefix well known to customers, such as “800,” “866”, or “877” and may be provided by businesses or other types of large organizations to encourage customers to call without incurring charges for the call. Furthermore, a toll-free “vanity” number may include an easy to recognize pattern or number which may be valuable to the business or organization for branding or as a direct response tool.
Voice communication is increasingly being implemented in a packed-switched Internet Protocol (IP) network through the use of Voice over IP (VoIP) technologies. VoIP may be implemented using Session Initiation Protocol (SIP). SIP networks may experience problems handling certain types of toll-free telephone calls.